A conventional energy conversion by solid biomass has been performed mainly based on heat utilization by direct combustion. In this case, advanced energy use is difficult. In the case of power generation for example, a wood chip boiler is used to generate water vapor to generate power by a water vapor turbine. This power generation method provides a power generation efficiency of 8 to 12% in the case of an actual plant of about 1000 to 3000 kW. Such a small-scale power generation of 100 kW cannot provide an output of electric power. At present, a gasification technology has been developed to use biomass energy with high efficiency. In the case of a conventional gasification technology, a partial oxidation process has been mainly used in which biomass is half-burned in an amount equal to or lower than a theoretical amount of air or oxygen. However, this process causes a large amount of soot and tar and also causes exhaust gas used for heat generation to be mixed in the generated gas, thus failing to provide generation of high-quality gas.
In order to realize an advanced use of biomass energy, the conversion to liquid fuel is ideal from the viewpoint of the use for automobile fuel and the transportation of the fuel. In the case of a method of manufacturing liquid fuel out of biomass however, both of ethanol fuel obtained by fermentation of carbohydrate and starch as raw material and BDF (bio diesel oil fuel) obtained by the esterification of vegetable oil by an addition of methanol are manufactured meinly out of food as raw material and thus provides a low yield per area under cultivation.
A practical apparatus as an objective of the present invention that can thermochemically gasify all biomasses, such as grass plants and woody plants, to convert the biomasses to chemically-synthesized raw material has been not yet developed.
In recent years, a floating external heat-type gasification method has been developed to obtain, out of biomass, clean fuel gas of a high calorie adapted to a power generation gas engine. The details of this method are disclosed in the following Patent Document 1, Patent Document 2, and Patent Document 3. Patent Document 1 discloses a biomass gasification apparatus in which a biomass burning space is separated from a biomass gasification space. This apparatus uses a high temperature complete combustion gas obtained from the biomass burning space to heat the biomass gasification space and also supplies the high temperature complete combustion gas to the gasification space through a plurality of through holes. By this apparatus, the heat generation reaction in the burning space and the endothermic reaction in the gasification space are separately controlled so as to gasify the biomass easily, thus providing high-quality fuel gas which has been impossible in the conventional technology. In the case of this apparatus however, uniformizing the generated gas from biomasses is realized by introducing the high-temperature combustion gas to the gasification space via the through holes. Due to this, disadvantages have been caused in that the generated gas is mixed with a large amount of carbon dioxide gas and nitrogen included in the high temperature complete combustion gas to cause a deteriorated quality of generated gas, generated gas and biomass as raw material of generated gas are dissipated, the distribution of gasification agent is uneven, and many fine pores must be processed for example.
Patent Document 2 and Patent Document 3 disclose a technology to supply water vapor to the gasification space. Although the above disadvantages are solved by the addition of water vapor, some technical problems including the following points that should be solved or improved remain unsolved.
The first disadvantage is that biomass as gasification raw material must be fine powders of about 3 mm or less and thus a high grinding power is required and coarse powders of 10 to 20 mm cause a trouble.
The second disadvantage is that the gasification agent supplied to the gasification space (e.g., water vapor) intrudes into a biomass supply hopper to cause dew condensation or to cause the biomass fine powders to contain a large amount of water. This consequently makes it difficult to smoothly supply the biomass fine powders to the gasification space, thus remarkably deteriorating the gasification efficiency in the gasification reaction room.
The third disadvantage is that a ratio of hydrogen in the composition of the resultant fuel gas is low and thus the resultant fuel gas is still insufficient as synthesis gas for synthesizing methanol or GTL for example.    Patent Document 1: Japanese Patent Publication No. 2002-88379 A    Patent Document 2: Japanese Patent Publication No. 2004-51717 A    Patent Document 3: Japanese Patent Publication No. 2004-51718 A